The present invention relates to a connector system for cardiac pacers and pacer leads and more particularly to such a system which permits the use of either a unipolar or bipolar lead.
In connection with the development of electrical cardiac pacing systems which stimulate a patient's heart to replace or supplement natural stimulation, a great variety of electrode systems have been developed for applying electrical energy to the patient's heart muscle. In general, these electrode or lead systems may be divided into two different categories. First, there are bipolar leads in which the lead itself carries two electrodes. One electrode is a stimulating electrode usually located at the distal tip of the elongate lead structure, and the other is a reference or indifferent electrode usually in the form of an annular conductive band spaced away from the distal tip of the lead. With such a bipolar electrode, current thus typically flows a relatively short distance in the patient's body. The second category includes unipolar leads. A unipolar lead includes but a single conductor terminating with the stimulating electrode at the distal end of the lead. The proximal end of the lead is connected to one side of the pulse generating circuitry within the pacer. A reference or indifferent potential is established by connecting the other side of the pulse-generating circuitry to a conductive wall of the pacer case which serves as the reference electrode. The pacer case itself is typically implanted some distance from the patient's heart, e.g., in the abdomen or in a subcutaneous pocket near the patient's shoulder. While the use of the pacer case affords a very large area of contact with the patient's body, the stimulating and sensing current path is relatively long.
Depending on circumstances, one or the other of these two general classes of electrode lead systems may be preferred. The same pacer electronics may, however, be usable in either case. It is thus highly advantageous to provide a system of interfacing the pacer electronics with the lead system in a manner which is flexible and can accommodate leads of either type. As will be understood, such an interfacing system minimizes the need for largely duplicative stocking and simplifies the replacement of pacer electronics at the end of battery life.
Among the several objects of the present invention may be noted the provision of a cardiac pacer incorporating a connector system which is usable with either a unipolar lead or a bipolar lead; the provision of such a system which permits the pacer case to be selectively utilized as an indifferent electrode; the provision of such a system which facilitates reliable connections to the lead utilized; the provision of such a system which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.